A contactor is an electrically controlled switch used for switching an electrical circuit or electrical device with high current ratings. The contactor is controlled by control circuitry having a much lower power level than the electric circuit or device that is being switched by the contactor. The contactor comprises contacts, i.e. the current carrying part of the contactor, and a mechanism (for instance an electromagnet or coil) for closing and opening these contacts. The contactor is normally a mono-stable remotely operated device, operated e.g. by the mentioned control circuitry. The contactor is built for handling millions of operations and is a very reliable and robust device for this purpose. However the contactor lacks means for providing a safe disconnection when being in open position, i.e. in a position disconnecting the electrical power circuit. Such safe disconnection is a requirement for ensuring that the contacts of the contactor will not close by mistake or by some malfunctioning, as this would be life threatening e.g. for a person servicing the electrical power circuit or device that is being switched by the contactor.
An example of a device for accomplishing such safe disconnection is a switch disconnector. The switch disconnector is normally a bi-stable hand operated device that is built for handling few operations. For instance, in case of emergency it can be used manually for breaking the current, and it can also provide a safe disconnection of the electric circuit or device. The switch disconnector normally lacks the robustness and reliability for handling millions of operations.
Because of their different characteristics the two types of devices, i.e. the contactor and the switch disconnector, are often used together to provide a reliable and safe installation. Traditionally, switching installations are hence built with contactors and switch disconnectors together. The contactor is used for switching the normal load currents while the switch disconnector is used for emergency switching and safe disconnection of the electric circuit or device.
The switch disconnectors are however expensive and may be difficult to operate. They may, for instance, require a fairly high strength if maneuvered by hand. If the switch disconnector is provided with means for remote operation, e.g. in the form of a motor drive, the arrangement of contactor and switch disconnector is rendered complicated as well as expensive. Examples of these known switch disconnectors are disclosed in DE 19538389 and EP2797097.